THE SIMILARITY BETWEEN CONTINUOUS AND DISCONTINUOUS PRECIPITATION

Precipitation mechanisms in Al-8wt%Mg and Cu-15wt%ln alloys have been studied, using X-ray diffraction and optical microscopy. Usually, disc ontinuous (cellular) and continuous precipitations are observed in Cu- In and Al-Mg systems respectively. A new lattice parameter variation a (t) containing characteristics of both precipitation types, the contin uous variation and the simultaneous existence of two values of a is fo und for Al-8 wt% Mg alloy. On the other hand, a discontinuous coarseni ng followed by spheroidization of lamellar structure in Cu-15 wt% In a lloy lead to more homogeneous precipitation identical with that observ ed in the last stages of ageing in Al-8 wt% Mg alloy.